Telomycin nanoparticles from Streptomyces abietis: Effects on hepatorenal function, antioxidant activity, immune responses, and histopathological and immunohistochemical alterations in African catfish (Clarias gariepinus) challenged with Staphylococcus aureus.

The present study investigated the antibacterial efficacy of telomycin nanoparticles (TNPs). Telomycin, a bioactive metabolite of Streptomyces abietis PP752347, was loaded onto chitosan nanoparticles. The minimum inhibitory concentration (MIC50) of telomycin against pathogenic strains of Staphylococcus aureus was determined to be 1.0 ± 1.00 μg/mL and 2.0 ± 1.00 μg/mL, respectively, against different strains. Meanwhile, the (MIC50) of TNPS against the same strains was .125 ± 1.00 μg/mL and 1.0 ± 1.00 μg/mL, respectively. Morphological changes in S. aureus treated with TNPS were examined using scanning electron microscopy (SEM). Additionally, the bioactive metabolite extracts were characterized using X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR), while SEM was employed to characterize the nanoparticles. For the in vivo experiment, 120 African catfish (Clarias gariepinus) were divided into four groups: the first group served as the negative control (neither challenged nor treated); the second group (TNPS) received TNPS treatment (100 μg/L); the third group (SA) represented the positive control, infected with S. aureus; and the fourth group (SA + TNPS) was infected with S. aureus and treated with TNPS. Infected fish (SA and SA + TNPS groups) received an intraperitoneal injection of S. aureus (1.6 × 106 CFU/mL). The findings demonstrated that all infected groups exhibited noticeable clinical signs resulting from S. aureus infection. TNPS administration via immersion significantly reduced the negative impacts of infection on liver and kidney biomarkers, innate immune responses, antioxidant levels, serum gonadotropic hormones, and hepatic expression levels of both Caspase-3 and TNF-α. TNPS treatment significantly (p < 0.05) alleviated S. aureus-induced clinical symptoms and hepatorenal dysfunction. It enhanced innate immunity (lysozyme, nitric oxide, MPO, and IL-1β expression), antioxidant capacity, and sex hormone levels, while reversing histopathological alterations in the liver, kidney, spleen, and ovaries. Furthermore, TNPs reduced hepatic expression of both Caspase-3 and TNF-α. These findings indicate that TNPs (100 μg/L) is safe for African catfish and exhibits potent antibacterial activity, supporting its potential as a promising and eco-friendly therapeutic agent for aquaculture.